1. Technical Field
The present invention relates to a projector that projects and displays an image on a projection surface.
2. Related Art
When an image is projected and displayed on a projection surface such as a screen, using a projector, a focus adjustment for adjusting a deviation of a focus (focus point) of an image projected on the projection surface (hereinafter, referred to as a “projected image”) and an adjustment such as a keystone correction for correcting a distortion in an image range of projected image (hereinafter, referred to as a “keystone distortion”) are generally performed due to a relative positional relation between the projector and the projection surface.
As disclosed in JP-A-2010-32842, for example, the focus adjustment is performed in such a way that a pattern image having a stripe shape in which a white line and a black line are alternately arranged is projected and a focal position of a focus lens is changed in order to increase a difference between a grayscale value of the white line and a grayscale value of the black line of the projected image which is captured (hereinafter, referred to as a “captured projected image”).
When the focus adjustment described above is performed, there is a case where the focus adjustment may be insufficient due to a projection state of a projector at a focus adjustment starting point, such as a relative positional relation between a projector and a projection surface, a deviation degree of a focus before the adjustment, a focal position of a focus lens before the adjustment, and a performance of an imaging camera. For example, when the resolution of the imaging camera is low or when the deviation degree of the focus is high, there are cases where a portion of a white line of a captured projected image is blackened, a portion of a black line of the captured projected image is whitened, the captured projected image is entirely whitened or the captured projected image is entirely blackened. In these cases, a difference between a grayscale value of a portion of the white line and a grayscale value of a portion of the black line of the captured projected image before the adjustment is originally small. Accordingly, even if the focal position of the focus lens is changed, the variation amount is also small, whereby causing a problem such as a difficulty in performing an accurate adjustment. Therefore, the focus adjustment is likely to be insufficient. In addition, a desirable focal position may become out of an adjustment range.